Epithelial ovarian cancer is the second most common gynecologic cancer. Because of poor survival for the majority of ovarian cancer patients, identification of factors contributing to disease progression is of utmost importance. Although a significant percentage of ovarian cancer patients respond well to initial chemotherapy, the success of treatment is limited by the development of chemo resistance, and the majority of patients relapse and die from recurrent disease. Our previous work has shown a variety of mechanisms by which biobehavioral factors (referring collectively to behavioral, social, and/or psychological factors and concomitant biologic processes) can directly affect key biological signaling mechanisms to enhance tumor growth and impair the immune response in ovarian cancer. Although the neuroendocrine stress hormones norepinephrine (NE) and cortisol have been shown to increase chemo resistance pre-clinically, little is known about the contribution of psychological and social processes to chemo resistance in the clinical setting of ovarian cancer. Based on compelling preliminary pre-clinical data in ovarian cancer, we propose that psychological and social processes and the neuroendocrine stress response will contribute to impairment of the chemotherapeutic response in ovarian cancer patients. Thus, this grant will focus on mapping psychological and social and neuroendocrine influences on disease progression in 178 women with high grade serous epithelial ovarian cancer, with particular attention to chemo resistance as a mechanism. This study is highly innovative as 1) contributions of biobehavioral processes to chemo resistance in human epithelial cell cancers in a clinical setting have not been examined, and 2) this is the first translational study using exosomes (tumor derived vesicles in peripheral circulation) to examine relationships between biobehavioral factors and tumor dynamics. Use of the exosome biomarker approach will provide a longitudinal window on tumor characteristics not otherwise available in the absence of repeated surgery. If initial response to chemotherapy could be enhanced or maintained for a longer duration, it could have substantial survival benefits. Thus findings that biobehavioral stress-related processes alter the response to chemotherapy would have significant implications for clinical management of ovarian patients, specifically the potential for adjunct use of behavioral or pharmacological interventions to delay the development of chemo resistance. Because chemotherapeutic response is closely linked to ovarian cancer survival, understanding biobehavioral impediments to maximum chemotherapeutic response is of great public health significance.